May 2, 2013

Just over three years ago, the Gulf Coast, still recovering from the devastating effects of 2005's Hurricane Katrina, awakened to the news their region was once again under imminent threat. The Deepwater Horizon disaster and oil spill spewed an estimated 4.9 million barrels of crude oil into the Gulf of Mexico over 87 days. Despite the feel good, BP-produced Gulf tourism commercials, the full effects of the spill will only be known thanks to the passage of time.

One such example of an ongoing negative effect, posted online in advance of publication in the journal Environmental Science and Technology, was conducted by researchers from Clemson University in South Carolina, Louisiana State University (LSU) and the University of California — Davis (UC Davis). Their findings show the effects of crude oil toxicity on populations of the common Gulf Coast killifish, an environmental indicator species. As an environmental indicator species, the killifish acts as a sort of ℠canary in the coal mine,´ serving a role as a predictor of health risks associated with a broader exposure.

The team found killifish embryos subjected to sediments from oiled locations in 2010 and 2011 presented developmental abnormalities. Among the abnormalities noted include heart defects, delayed hatching and reduced hatching success. This current study and its findings are a component of an ongoing collaborative effort designed to catalogue and track the impacts associated with the Deepwater Horizon oil spill. The researchers focused their efforts on documenting killifish populations in areas of Louisiana that received markedly heavy amounts of oil.

The killifish occupies habitats similar to those populated by species like redfish, speckled trout, flounder, blue crabs, shrimp and oysters. For this reason, the research team speculates these other species may be at risk of experiencing similar effects.

“These effects are characteristic of crude oil toxicity,” according to co-author Andrew Whitehead, assistant professor of environmental toxicology at UC Davis. “It´s important that we observe it in the context of the Deepwater Horizon spill because it tells us it is far too early to say the effects of the oil spill are known and inconsequential.” He continues, “By definition, effects on reproduction and development — effects that could impact populations — can take time to emerge.”

One of the reasons the killifish is an excellent study subject, in addition to its role as an environmental indicator species, is due to their abundance in the coastal marsh habitats common in the region. Researchers said the nonmigratory behavior of these fish makes it important to get measurements of their health because it translates to the overall health of the environment.

Lead author Benjamin Dubansky, himself having only just earned his PhD from LSU, commented, “Our findings indicate that the developmental success of these fish in the field may be compromised.”

However, as Whitehead points out, their findings may predict longer-term impacts to killifish populations. As the oil from the spill made landfall in patches, rather than coating the coastline, some populations of killifish may have experienced higher levels of crude oil toxicity than others. According to Whitehead, it is entirely possible some of the healthier, less impacted populations of killifish could, for the species as a whole, act as a form of buffer against the negative effects of the spill.

The research study received grant funding from the National Science Foundation (NSF), the Gulf of Mexico Research Initiative and the National Institutes of Health (NIH). The series of studies on killifish populations have been ongoing since the spill occurred in April 2010.

Whenever a major environmental crisis occurs, it is important to remember that when the immediacy of the crisis comes to an end, knowledge of the long-term effects is still a long way off. Work done by research teams help us to better understand the impact of a disaster and hopefully lead us to learn of better ways to cope with disasters in the future.

Image Below: This Gulf killifish embryo was exposed to oiled sediments from the 2010 Deepwater Horizon spill. Three years later, killifish continue to show health defects related to oil toxicity from the spill. Credit: Benjamin Dubansky